The research objectives described will, as heretofore, comprise a broad program in which special emphasis is placed upon the elucidation of the cell-mediated and the humoral antibody-mediated components of transplantation immunity, and their interactions in the phenomenon of enhancement, in host-versus-graft and graft-versus-host situations, in allogeneic pregnancies, and when certain kinds of allografts, notably those of lymphoid cells, are placed in the anterior chamber of the eye. Analysis of the immunobiologic aspects of the maternal-fetal parabiotic relationship will continue with particular emphasis upon the phenomenon of maternally induced runt disease and tolerance, using zygote transfer where appropriate. Preliminary findings that infant rats absorb in a viable form lymphocytes and other cells via the maternal milk - i.e. natural adoptive immunization - will be subject to confirmation in a variety of rat strain combinations as well as in mice. Work will continue to determine the biological role of the non- antibody immunoglobulin elicited by specific antigenic challenge, using in vitro approaches which will allow identification of the cellular participants in the response. Despite the apparent diversity of these objectives, they nearly all bear upon the question as to how specific genes produce their effects, and upon the interaction between cellular and humoral immune responses and their regulation.